About using namespaces

[tron.thomas]

If I remember correctly, in one of his books, Scott Meyers suggests
putting code into a custom namespace rather, and here I might be
paraphrasing, "polluting the global namespace" with type definitions
and such.

Assuming this is a good idea, I'm wondering about what happens when so
many people do the following:

using namespace std;

It seems like such a statement will bring a lot of stuff into the
global namespace, and a lot of it won't be used at all. Most people
only make use of a small portion what contained in the std namespace.

I'm wondering if it isn't better to only declare what someone wants to
use such as:

using std::vector;
using std::cout;

What kind of difference can it make to use either approach for
promoting items for a specific namespace for use in global scope?

[Daniel T.]

tr*********@verizon.net wrote:

If I remember correctly, in one of his books, Scott Meyers suggests
putting code into a custom namespace rather, and here I might be
paraphrasing, "polluting the global namespace" with type definitions
and such.

Assuming this is a good idea, I'm wondering about what happens when so
many people do the following:

using namespace std;

It seems like such a statement will bring a lot of stuff into the
global namespace, and a lot of it won't be used at all. Most people
only make use of a small portion what contained in the std namespace.

I'm wondering if it isn't better to only declare what someone wants to
use such as:

using std::vector;
using std::cout;

What kind of difference can it make to use either approach for
promoting items for a specific namespace for use in global scope?

If "using namespace /X/" is contained within an individual translation
unit (a .cpp file) then it is a rather local "pollution" that can be
easily changed (assuming you aren't writing .cpp files that are
thousands of lines long.)

However putting using declarations or definitions in header files have a
much wider effect.

[Victor Bazarov]

tr*********@verizon.net wrote:

If I remember correctly, in one of his books, Scott Meyers suggests
putting code into a custom namespace rather, and here I might be
paraphrasing, "polluting the global namespace" with type definitions
and such.

Assuming this is a good idea, I'm wondering about what happens when so
many people do the following:

using namespace std;

It seems like such a statement will bring a lot of stuff into the
global namespace, and a lot of it won't be used at all. Most people
only make use of a small portion what contained in the std namespace.

I'm wondering if it isn't better to only declare what someone wants to
use such as:

using std::vector;
using std::cout;

What kind of difference can it make to use either approach for
promoting items for a specific namespace for use in global scope?

I believe there is a FAQ on that. See 27.5.

V
--
Please remove capital 'A's when replying by e-mail
I do not respond to top-posted replies, please don't ask

[tron.thomas]

On Oct 28, 9:23 am, "Victor Bazarov" <[e-mail]:

[e-mail] wrote:

If I remember correctly, in one of his books, Scott Meyers suggests
putting code into a custom namespace rather, and here I might be
paraphrasing, "polluting the global namespace" with type definitions
and such.

Assuming this is a good idea, I'm wondering about what happens when so
many people do the following:

using namespace std;

It seems like such a statement will bring a lot of stuff into the
global namespace, and a lot of it won't be used at all. Most people
only make use of a small portion what contained in the std namespace.

I'm wondering if it isn't better to only declare what someone wants to
use such as:

using std::vector;
using std::cout;

What kind of difference can it make to use either approach for
promoting items for a specific namespace for use in global scope?

I believe there is a FAQ on that. See 27.5.

V
--
Please remove capital 'A's when replying by e-mail
I do not respond to top-posted replies, please don't ask

Where can the FAQ be found?

[=?UTF-8?B?RXJpayBXaWtzdHLDtm0=?=]

On 2007-11-02 02:49, tr*********@verizon.net wrote:

On Oct 28, 9:23 am, "Victor Bazarov" <[e-mail]:

>[e-mail] wrote:

If I remember correctly, in one of his books, Scott Meyers suggests
putting code into a custom namespace rather, and here I might be
paraphrasing, "polluting the global namespace" with type definitions
and such.

Assuming this is a good idea, I'm wondering about what happens when so
many people do the following:

using namespace std;

It seems like such a statement will bring a lot of stuff into the
global namespace, and a lot of it won't be used at all. Most people
only make use of a small portion what contained in the std namespace.

I'm wondering if it isn't better to only declare what someone wants to
use such as:

using std::vector;
using std::cout;

What kind of difference can it make to use either approach for
promoting items for a specific namespace for use in global scope?

I believe there is a FAQ on that. See 27.5.

Please do not quote signatures.

Where can the FAQ be found?

Normally it can be found at http://www.parashift.com/c++-faq-lite/
though here have been some DNS problems so if that does not work try
http://www.coders2020.com/cplusplus-...ned/index.html

--
Erik Wikström